BirdAnalyst
Species · Louisiana · BBS 2025 Release · 1966–2024

Least Bittern Population Trend in Louisiana

All statesWetland birds

Least Bittern in Louisiana has surged: up 302% on the route-weighted index since 1970.

+302%Since 1970TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
18Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
50YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Least Bittern Trends in LouisianaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc increasecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Least Bittern has surged in Louisiana: up 302% on the route-weighted index since 1970.

Least Bittern Population Forecast in Louisiana

If the recent trend holds, Least Bittern in Louisiana is projected to fall about 42% by 2029 — from 0.95 in 2024 to a central estimate of 0.55 (95% range 0.12–0.98). A 5-year backtest shows a typical error of ±47.4%, with 80% of held-out values landing inside the 95% band.

-42%Change by 2029TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
0.55Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.12–0.9895% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±47.4%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Least Bittern in Louisiana is projected to fall about 42% by 2029 — from 0.95 in 2024 to a central estimate of 0.55 (95% range 0.12–0.98). A 5-year backtest shows a typical error of ±47.4%, with 80% of held-out values landing inside the 95% band.19672029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20250.520.090.95
20260.530.100.96
20270.540.100.97
20280.540.110.97
20290.550.120.98

Least Bittern Survey Routes in Louisiana

Routes recording Least Bittern in Louisiana.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Forked Island3220242008
Forked Island 21920112010
Ltl Chenier720241986
Sabine Nwr 2520172009
Sabine Nwr420081989
Kaplan420222008
Creole319801970
Ltl Chenier 2320112010
Grand Isle220192013
Esther220232021
Ramah120232010
Maurice120102010
Belair120172017
Gran Chenier119821967
Lacombe119691969
Hackberry120161971
Shaw120212021
Glencoe120122011

Least Bittern Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaillinoisindianaiowakansasmarylandmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooregonsouth-carolinasouth-dakotatexasvermontvirginiawisconsin

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.